1. Field of the Invention
The present invention relates to a security system for monitoring persons aboard a vessel using radio frequency identification (RFID), and more particularly, to a security system for automatically detecting and signaling the event of a person falling overboard from a vessel into a body of water. Said security system also provides the exact time and location of the event for facilitating the rescue of said person.
2. Background
Traveling in a boat, cruise ship or other vessel is very popular but it can be risky. More often people on cruise ships disappear or fall overboard. In both instances, the event occurs without anyone noticing until it is too late. The likelihood of a successful rescue depends on the quickness of detecting said person overboard. Therefore, there is a need for an improved security system that can automatically detect and signal when a person falls overboard from a vessel, and that can determine the exact time and location of said event in order to rescue said person.
Various systems have been developed to detect a person overboard. Most of these systems rely upon the use of a transmitter attached to a person who has fallen overboard to send a signal (ultrasonic waves, radio waves, acoustic signal, or electromagnetic signal) through air or water to a receiver onboard the vessel when said transmitter is immersed in water. See U.S. Pat. Nos. 4,305,143; 5,463,598; 5,021,765; and 5,886,635. The success of these systems depends on producing a signal of sufficient strength that can travel through air or water to reach the receiver on the ship.
Other systems rely upon continuously monitoring a signal transmitted by a transmitter attached to each person onboard a vessel. When the transmission of the signal is terminated upon entry of the transmitter into water, an alarm is triggered. See U.S. Pat. Nos. 4,549,169; and 6,057,759. Systems that depend on the interruption of a signal are impractical for vessels with large numbers of people on board. This is due to the fact that: 1) each transmitter would have to be active at all times, thus requiring a large amount of power supply; and 2) the receiver would have to be monitoring each individual signal at all times, thus requiring an excessively complex receiver.
A common deficiency to all the systems explained above is that the transmitter, and eventually the man overboard alarm system, is triggered upon immersion of the transmitter in water. People on boats, cruise ships or other vessels like to swim in the pool or at the beach. In those circumstances, where no risk of a person overboard exists, the transmitter would be immersed in water and said receivers would recognize such immersion as a person overboard thus causing false alarms.
Another system that has been developed to detect a person overboard relies upon the use of several infrared (IR) sensors which are placed surrounding the hull of a vessel. The IR sensors produce light beams which are detected by another IR sensor. When a person falls overboard, he passes through the sensors breaking the light beam. The light beam interruption triggers an alarm. See U.S. Pat. No. 7,335,077. A deficiency of this system is that objects other than a person overboard (e.g., water or a bird) can pass through the IR sensor, breaking the light beam, and thus activating the alarm. False alarms will cause the crew to react more slowly in the event of a real emergency. Also multiple activations of the alarm system by accident would be very unpleasant for the passengers aboard the vessel.
Therefore, there is a need for a security system that can detect a person overboard more accurately, that does not depend upon immersion of the activation device in water, and that would not be triggered by accidental or false alarms.